Chemistry of aryloxide compounds of titanium in oxidation states +4, +3 and +2
Abstract
A variety of titanium homoleptic aryloxide, heteroleptic haloaryloxides and heteroleptic alkyl-aryloxides have been prepared. Spectroscopic and structural studies show that the use of 2,6-dialkyl-phenoxides leads to monomeric species, while use of relatively less bulky phenoxides allows the formation of dimeric species. The bis(alkyl), bis(aryloxide) compounds, Ti(OAr)$\sb2$R$\sb2$, which have been prepared undergo migratory insertion reactions with alkyl and aryl isocyanides. Both mono(iminoacyl) and bis(iminoacyl) products have been isolated. Spectroscopic and structural investigations show that the iminoacyl ligand binds in a dihapto fashion. Dihapto-iminoacyl compounds undergo facile intramolecular coupling reactions. This gives rise to enediamide and enamidolate compounds containing a bent metallacyclic ring. Several of these compounds have been isolated and characterized structurally and spectroscopically. The reduction behavior of the Ti(IV) compounds prepared was probed by electrochemical and chemical techniques. Electrochemically they all show readily accessible reduction waves. Discrete Ti(III) species have proved to be observable by EPR, but difficult to isolate. Three compounds which have been isolated are Ti(OAr-2,6Ph$\sb2)\sb3$(NMe$\sb3$), (thf) $\sb2$Na (Ti(OAr-2,6Pr$\sp{\rm i}\sb2)\sb 4\rbrack$ and Ti(OAr-2,6Pr$\sp{\rm i}\sb2)\sb3$(py)$\sb 2$. Organometallic pathways starting from mono(iminoacyl) compounds or a bis(alkyl) compound lead to low valent titanium products. These pathways have been shown to involve alkyl transfer and/or reductive elimination steps with Ti(II) species being the key intermediate. Supporting reactions have been carried out with Zr, Th, V and Nb compounds. This chemistry leads to a variety of homoleptic and heteroleptic compounds.
Degree
Ph.D.
Advisors
Rothwell, Purdue University.
Subject Area
Chemistry
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